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  1. #8
    Senior Member lostboy's Avatar
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    Quote Originally Posted by SteveE View Post
    Well it did when I was learning. That was the single best piece of advice I ever got.
    It's possibly the single biggest load of ******** ever spoken by any "guru" and seems to be making a rather unfortunate resurgence. Think about the basic physics of where your rig wants to go when sheeted in and then work out how much "pressure" there is on the MF, or just look at any Boge joint when you're sailing along and it'll give you the answer.
    Got an opinion? Great. Guess what, so's everyone else!

  2. #9
    Quote Originally Posted by kpdunn View Post
    Hi there, I have been out on the water only about 6 or 7 times at a sailing school on a 220L with daggerboard.
    Last night I had a turn on a JP Freeride 145 / 6.0m in very light wind and did get going eventually after some trial/error/sinking.

    I immediately noticed a lot of drift and from reading forums on this site I gather this is due mostly to the lack of a daggerboard.

    However one thing I want to get advice on, is when tilting the rig to the bow to turn downwind - the board very definitely turned upwind, one time blowing me off !

    It happened twice I think both times when the wind was powering the side of the sail where it wraps around flat over the mast, (apologies if there is a name for that). I doubt if that is significant though.
    Any idea what I am doing wrong, or do I need to go learn the theory regarding pressures etc properly.
    I am about 5'9" and 75kg

    Thanks in advance


    So what happened was you were used to a board with a daggerboard and then changed to a board which has just a fin to keep it from slipping sideways. The difference is that the fin is at the back of the board, whereas a daggerboard is in the centre. That change makes the board more 'turny' and less 'directional'. The JP145 is also a much smaller board (and a 'shortboard').

    So what happens is you climb on the board and get hold of the rig and that means your body weight and the pull of the rig are both putting a sideways load on the hull. If there's too much load on the back of the board, the tail drifts downwind, meaning the board nose turns into wind. Everybody experiences that problem when starting out – we step on the back of the board and the board tail slews off downwind..

    As you rightly say, to counteract that sideslip at the tail, you would normally dip the rig forward to allow wind to push the nose of the board downwind – and the aim is for tail slide and nose slide to be in equilibrium, which then allows the power of the rig to drive the board forwards in a straight line. As the board starts to move forward, it then stops slipping sideways (and so a daggerboard is not needed).

    But what has happened here – from your description – is you stepped on the board and the tail slewed downwind, and when you put the rig forward it sounds like you were already 'head to wind' and went into a tack before the wind could push the nose downwind. The wind was on the wrong side of the sail, so you probably fell in backwards.

    This stuff is straight forward enough, but difficult to put into simple words and without pictures on a forum.



    What you need to do now is simply to go and try again (and usually most get the hang of it, or you could get help from an instructor). Once you can get the board moving forwards, in a straight line, then the board won't slip sideways so much.


    You don't actually have to dip the rig forwards that much. Just stand further forwards on the board and once you have the rig upright, 'sheet in' with your back hand. The sheeting in powers up the rig so that sideways load is applied to the board via the mast foot, and, in terms of stabilising the board from turning, that counteracts the sideways load on the tail of the board from your body weight.


    Once you get going, you then need to get a feel of the rig – so that wind power directs the board forwards by what many people call 'mast foot pressure' or MFP. Unlike a dinghy with a fixed mast and stays, a windsurf rig is very moveable via the universal joint (mast foot). So the rig loads on a windsurfer are actually transferred to the board via three points – the mast foot and also via your legs as they stand on the board. Those three points are spread along the board so to turn downwind you usually need to direct the rig load via the mast foot and via your front foot.
    Last edited by basher; 10th September 2015 at 09:32 AM.
    Now back in the UK.

  3. #10
    Having read some other responses on here – mostly good – I see there is also some dispute as to whether mast foot pressure (MFP) exists or not.
    Let's try and put that one to bed quickly, before it kicks off.

    On a windsurfer, there are two basic loads – those coming from the rig and those coming from our body weight as it's shifted about the board.
    Because a windsurf board has no fixed mast or stays, the only way in which the rig load can be applied to the board is via the three points of contact – namely the mast foot (or U/J) and via our two legs. We feel the rig load in our hands via the boom, and that load transfers down our legs to the board to drive it along. Part of the rig load also goes down the mast foot. There are no other ways in which the rig power can be applied to the board.

    So it's mast foot, front foot and back foot. We use the pivot of the U/J to allow the rig load to move back or forwards along the board, and we vary the load on the board, front to back, via the mast foot, front foot, and back foot.

    The resultant load from all three then acts over the sideways resistance of the board – whether at planing or displacement speeds. At displacement speeds (on a shortboard we call this 'slogging') the sideways resistance with a shortboard comes from the hull friction in the water, from a rail sunk in the water, and from the physical area of the fin. At planing speeds, the sideways resistance comes from fin 'lift' and partly from spray being ejected from the rail at the tail.
    We adjust the rig fore-and-aft to allow the rig power to sit in equilibrium over the sideways resistance of the hull at any moment to keep the board driving in a straight line. At planing speeds, we rake the rig back more because the sideways resistance is further back. In sailing, this is traditionally described as getting the centre of effort over the centre of lateral resistance (C of E over C of LR).


    The reason I don't like the term 'mast foot pressure' is it implies the weight of the rig acts downwards on the hull (which it partly does) and that misses the fact that a lot of the rig load acts SIDEWAYS through the mast foot. People still think in old fashioned terms of a weighty rig acting to 'hold the nose down' when in fact once you are moving forwards most of the load is a sideways one. We might rename mast foot pressure as 'mast foot leverage'.

    And in fact at planing speeds once you are fully in the straps, a lot (or most?) of the rig load is down your legs and not transferred to the board via mast foot pressure. The mast foot, and your two legs form a tripod-like structure which connects the rig load to the board.
    Don't be fooled if you look at your U/J and it seems to be pushing upwind or towards the windward rail – that's the cantilever effect of the rig you are holding in your arms, and is a force within a force. Despite the illusion, the rig load and resultant drive is still acting via the mast foot in a forwards and sideways way.


    When learning however, you can get too bogged down with this sort of intellectual discussion of what is happening with sail forces. It's far better to learn windsurfing skills through practice – just as you did when learning to walk or when learning to ride a bike.

    The basic idea you need know is that the act of sheeting in applies a forward load from the rig which pulls forwards and sideways, and that acts on the board via the mast foot to stop you slewing into wind. Sheeting in applies mast foot pressure on the nose of the board and that helps take weight off your legs.
    Last edited by basher; 10th September 2015 at 12:18 PM.
    Now back in the UK.

  4. #11
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    Quote Originally Posted by lostboy View Post
    ... just look at any Boge joint when you're sailing along and it'll give you the answer.
    It'd be interesting to put some sort of strain gauge into one of those North boingy extensions.

    Back to the OP, the problem might just be that you aren't doing what you think you are doing, or at least not as much as you think. Tilting the rig to the front of the board should turn the nose away from the wind but not if you have already headed upwind too far, or if you haven't sheeted in sufficiently. Tilting the board with your feet can also affect steering in light wind if you are going slowly. Generally I think luffing up is a result of a lack of commitment that passes with time.

  5. #12
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    OP - I used to be an instructor and saw this quite a lot, especially when people started to get a bit more power than the small beginner sails.

    Getting the board downwind does mean you lean the rig forwards, but also you need to do two more things:

    1. You also need to sheet in (pull in with the back hand). What happened to you is that you didn't sheet in, and the sail ended up pushing you the wrong way. The reason people don't sheet in is because it powers the sail up more than they are used to and pulls them off balance. You need to get your weight back simultaneously to counteract it.

    2. You also need to get the rig across your body, out in front of you. So not only does the mast tilt towards the nose, it tilts a bit towards the wind too. Again, this powers up the sail and you must anticipate by getting your weight back otherwise you wil get pulled over.


    Even though I've put them 1 and 2, 2 actually comes just before 1. Do these and you will turn downwind, even when powered up.

  6. #13
    Super Moderator na-omi's Avatar
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    Also try to get a sense of how much weight you have on your back and front feet... in addition to pointing your front foot forward to help direct the board, you also need to make sure you are 'pushing' with the front foot, and not hoofing the tail of the board downwind (hence pushing the nose through the wind as Basher explained) with a heavy back foot. I had this problem when I changed down to a 'shortboard' from a dagger-boarded longboard too You'll be needing to develop more sensitive foot- as well as rig-steering to sail these boards effectively.

  7. #14
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    As other have said, just point the front foot towards the nose of the board.
    If you draw a direct line from your front foot, it should be way in front of the mast foot. If it's behind you will be pushing the back of the board downwind and in turn the front of the board upwind.

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